given that $\displaystyle (x+b)(x+a)=(x+2)^2-9$, find the value of a and b
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Originally Posted by Punch given that $\displaystyle (x+b)(x+a)=(x+2)^2-9$, find the value of a and b $\displaystyle x^2 + (a+b)x + ab = x^2 + 4x + 4 - 9$ compare the coefficients of x^2, x and constant. Then solve for a and b.
It's easier to factorise the RHS using DOTS $\displaystyle (x + 2)^2 - 9 = (x + 2)^2 - 3^2$ $\displaystyle = (x + 2 + 3)(x + 2 - 3)$ $\displaystyle = (x + 5)(x - 1)$. What do you think $\displaystyle a$ and $\displaystyle b$ are?
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